1. Field of the Invention
The present invention relates to analog-to-digital converters, and more specifically to synchro-to-step data converters useful for driving step motors.
2. Description of the Prior Art
Synchro transmitters are electromechanical devices having a rotor and a plurality of stator windings for transforming an angular-position input into an analog electrical output, whereas step motors are electromechanical digital data input devices which convert electrical pulses into proportionate mechanical movement. Since synchro transmitters are analog data output devices, and since step motors are digital data input devices, there is a need for a converter whenever it is desired to use synchro data output to position a step motor. The requirement of synchro-to-step data conversion is frequently encountered in the art of shipboard navigation systems in which gyrocompasses having synchro data output are operatively coupled to repeaters, radar equipment, and autopilots designed for step data input. Such systems may typically utilize 360x (1 revolution per degree of heading) torque synchro data transmission from the gyrocompass and may typically have repeaters, radar equipment and autopilots which require step data that completes one cycle per degree of heading. Such step data will be called `360x` herein, even though, the actual step motor shaft, if the motor is of the 2-pole variable reluctance type, will rotate at 180X with respect to heading. The data conversion requirement is often further complicated when the gyrocompass of one manufacturer is operatively coupled to the step data input device of another manufacturer, since different manufacturers typically utilize different types of synchro data output and/or step data input.
A synchro-to-digital converter well adapted to convert synchro data at a predetermined voltage and frequency to a three bit binary code is disclosed in U.S. Pat. No. 4,031,531, entitled "Synchro-to-Digital Converter", and assigned to the Applicants' assignee. The above referenced converter is designed such that each of the output signals from a synchro device is applied to an individual voltage comparator through a step-down transformer. Each comparator is biased to a predetermined threshold level and produces an output signal whenever the magnitude of the associated synchro signal exceeds the threshold in the proper polarity. The comparator output voltages are applied to individual clocked flip-flops so as to produce three binary output signals in a parallel format indicative of the rotor displacement of the synchro device. The above described converter, however, is not designed to convert one of a plurality of different synchro data outputs into one of a plurality of different step data inputs.
Accordingly, there is a need for a synchro-to-step data converter which is capable of performing conversions among the various types of synchro data outputs and step data inputs. In the shipboard navigation systems are, for example, there is a particular need for such a device since it would provide for the efficient operative coupling of gyrocompasses providing 360x or other high transmission speed synchro data output and step data input equipment manufactured by different manufacturers which heretofore have been considered incompatible without the costly design of a unique converter limited to a particular application.